OFFSET
0,220
COMMENTS
The first term > 1 is a(219) = 2. - Michel Marcus, Apr 23 2019
LINKS
FORMULA
a(n) = [x^n y^4] Product_{k>=1} 1/(1 - y*x^(k^3)). - Ilya Gutkovskiy, Apr 23 2019
MAPLE
N:= 100;
A:= Array(0..N);
for a from 1 to floor(N^(1/3)) do
for b from a to floor((N-a^3)^(1/3)) do
for c from b to floor((N-a^3-b^3)^(1/3)) do
for d from c to floor((N-a^3-b^3-c^3)^(1/3)) do
n:= a^3 + b^3 + c^3 + d^3;
A[n]:= A[n]+1;
od od od od:
seq(A[n], n=0..N); # Robert Israel, Aug 18 2014
A025457 := proc(n)
local a, x, y, z, ucu ;
a := 0 ;
for x from 1 do
if 4*x^3 > n then
return a;
end if;
for y from x do
if x^3+3*y^3 > n then
break;
end if;
for z from y do
if x^3+y^3+2*z^3 > n then
break;
end if;
ucu := n-x^3-y^3-z^3 ;
if isA000578(ucu) then
a := a+1 ;
end if;
end do:
end do:
end do:
end proc: # R. J. Mathar, Sep 15 2015
MATHEMATICA
r[n_] := Reduce[0 < a <= b <= c <= d && n == a^3+b^3+c^3+d^3, {a, b, c, d}, Integers];
a[n_] := Which[rn = r[n]; rn === False, 0, rn[[0]] === And, 1, rn[[0]] === Or, Length[rn], True, Print["error ", rn]];
Table[a[n], {n, 0, 107}] (* Jean-François Alcover, Feb 26 2019 *)
CROSSREFS
KEYWORD
nonn
AUTHOR
EXTENSIONS
Second offset from Michel Marcus, Apr 23 2019
STATUS
approved